Stylus



Patented June 28, 1949 STYLUS Gregory Halpern, New York, .N. Y.,assignomto Polychrome Corporation,

poration of New York Application September 21, 1946, SeriWlNoi698j545 15Claims.

This invention relates to a stylus adapted to be heated and to inscribemarkings on a heatsensitive surface.

Heat-sensitive surfaces of the type under discussion generally comprisea fabric Web such as paper upon which a heat-sensitive coating isapplied, thecoating being of such a chemical composition that as heat isapplied to any portion thereof, it decomposes and its color changes.Such heat-sensitive surfaces are used for a variety of purposes, themost common of which is as a recording medium for use in cardiographicand encephalographic apparatus.

In such instruments, a stylus of low inertia is caused to vibrate inaccordance with amplifications of electrical impulses generated eitherby the heart or the'brain and the heat-sensitized paper is caused tomove under the stylus at a predetermined rate, themarkings which thestylus leaves on the paper thus corresponding to the detected electricalimpulses. Styluses for use in such apparatus must therefore have anexceedingly low inertia since they must be responsive to rapidly varyingimpulses of relatively small intensity. The styluses must at the sametime be heated to a temperature at their point of contact with theheat-sensitized surface sufficient to cause chemical change in thatsurface or in the coating thereon, the chemical-change resulting in theinscribed marking.

As employed heretofore, the stylus element has been shaped from a :thinelement of high resistance wire, usually a suitable nickel-chromium al-10y, and an electrical current is passed through the wire for heatingpurposes. However, the interaction between the wire and the chemicalcompounds of the heat-sensitized surface has been such as to affect thestylus to render it capable of use over but a small period of time.These deleterious effects-have primarily arisen because theheat-sensitive compounds generally include compounds of sulphur, lead,chromium, cobalt, iron, nickel or copper. When these compounds areexposed to heat so that their temperature is raised to approximately 800C., as by action of the stylus, they decompose to form the markings onthe surface and their products of decomposition include the oxides, andwhen sulphur is present, the sulphides of the metals above enumerated.These oxides and sulphides are generally characterized by having anexceedingly high melting point. Residues of these oxides and sulphides.tend to adhere :to the stylus and, because of the chemical compositionof the wire stylus, apparently tend :to. be adsorbed thereby and toYonkers, 'N. sY a-cor- 2 some'extent to enter into chemical combinationtherewith, and-uItimat'elyLbuiId up to considerable size.

A-number'of deleterious efiects stem from this, which effects bothsingly and cumulativelyhave made the employment 'ofsuchstyluseswithheatsensitized paper commercially impracticable. Amongsucheffects-maybementioned the followmg:

(1) As the oxide and sulphide decomposition products builduponthesurface of the stylus at the point where it contacts theheat-sensitized surface, they'aot to form an insulatory layer betweenthestylus'and the heat-sensitized surface. Hence, in order =to bring theheat-sensitized surface to its required marking temperature, the styluswire must be heated to-a temperature higher than that normallynecessary. Although the stylus wire has :desirable air characteristics,that is to say, it isresistant to progressive oxidation even when heatedto relatively high temperatures, as'its temperatureincreases,itsresistance to oxidation and corrosion decreases.

Consequently, the presence of the thermal decomposition products on thestylus-causes a reduction-in resistance to oxidation on the part of thestylus wire and thus a material decrease in effective life results.

(2) The decomposition productsthemselves appear toenter-into-chemicalcombination with the stylus wire. The exact'nature of this combinationis not'known butiithas beenobserved that in the presence of thedecompositionproducts the stylus-wire'deteriorates at afar greater ratethan Wouldbeexpected from oxidationalone and that the deteriorationtakes placemost rapidly at those points where-the residues have attachedthemselves.

-(3) As the residues build themselves up into bead-like form, themarkingseffected by the stylus-becomes scratohedt-blurred anddiscontinuous.

The aboveeffects have:thereforetended to restrictthelife ofthe=heatedsty1uses as heretofore known to approximately twentyminutes toonehalf hour-of continuous use.

As'has been state'd,'the residues formed have exceedingly "high fusionpoints, generally varying between 1,004? and l',40'0 C. and hence willnot liquify and fall from the stylus wire until heated to those hightemperatures. In addition, their tendency to enter" into chemicalcombination or amalgamation-with the stylus wire requires that=they beheated' well above their fusion points "before they "can 'be removed.

I have discovered' that the above disadvantages can be minimized andwell nigh eliminated by forming the stylus member of a hard abrasiveresisting substance having a high fusion point and which is relativelychemically inert, particularly with respect to the heat-sensitivecomponents of the surface over which the stylus is moved. t has beenfound that the life of such a stylus is relatively independent of itslength of use and is limited only by the life of the heating elementemployed in conjunction therewith. That heating element, as will appearhereinafter, may be sealed from external oxidizing, corroding or otherdeteriorating influences, and thus a stylus is produced which may beemployed with conventional heat-sensitive surfaces over extended periodsof time without material decrease in effectiveness. By the employment ofsuch a stylus, I have made practical from an economic point of view theutilization of heat-sensitive surfaces,

particularly in delicate recording instruments,

heretofore considered unfeasible because of the poor characteristics ofprior styluses.

To the accomplishment of the foregoing objects and such other objects asmay hereinafter appear, the present invention relates to a two-pieceheated stylus as set forth in the appended claims and as described inthis specification, taken together with the accompanying drawings, inwhich:

Fig. 1 is a side view of one embodiment of my stylus; and

Fig. 2 is a side cross-sectional view of another embodiment thereof.

This application is a continuation in part of application, Ser. No.676,547, filed June 13, 1946, by the present inventor, now abandoned.

My stylus comprises essentially a heat absorbing and transmitting stylusmember A and a heating element B therefor, the latter preferably beingin the form of a high resistance wire 2 which has good aircharacteristics, that is to say,

resists progressive oxidation even when heated to high temperatures.While a nickel-chrome alloy is preferably used, it will be understoodthat any of the well known wire elements having this characteristic maybe employed in its stead.

The heating element B is placed close to and preferably in contact withthe stylus member A, the heat from the heating element B being thustransferred to and absorbed by the stylus member A, the member A in turntransferring that heat via its tip 4 to the heat-sensitized surface overwhich it is caused to travel by any conventional mounting means (notshown).

In order to eliminate the deleterious effects upon the stylus which thedecomposition products of the heat-sensitized surface have heretoforeexerted, I have found it desirable to form the stylus member A of a hardabrasive-resistant substance which is either infusible or has a veryhigh fusion point and which is relatively chemically inert, particularlywith respect to the heat-- sensitive components of the surface. Manysubstances having these properties and which may be shaped to act as astylus are known in nature or are synthetically procurable. Gems, bothsemiprecious and precious, and either natural or artificial, conform tothe above specifications. In particular, I have found that sapphire anddiamond are exceptionally well suited to use in many styluses bothbecause of their ready procurability, their desirable physicalcharacteristics and their ability to be synthetically formed. Asynthetic sapphire (aluminum oxide or corundum) has been used by me withexceedingly fine results. Among compounds suitable for the purpose heredescribed but not classifiable as gems I may mention silicon carbide,elemental silicon or boron, compounds thereof, and oxides, borides,carbides, selenides, carbonates, tungstates, molybdates, silicates,silicides and sulfides of vanadium, chromium, iron, cobalt, nickel,tungsten, molybdenum, manganese and tantalum, where such chemicalcombinations are found to exist.

By employing a stylus member A formed of any one of the compositionsabove described, I achieve the following effects:

(1) The stylus member A being relatively chemically inert, it may beheated to any desired temperature without substantial danger ofdestruction through oxidation or corrosion. Thus, no matter to whatextent decomposition residues may accumulate on its tip 4 and act as athermal insulation, it can still be heated to a temperature sufficientto ensure good marking on the heatsensitive surface.

(2) Because of the inertness of the stylus member A to the decompositionproducts of the heat-sensitive surface, these products do not tend todecompose and destroy the stylus.

(3) Because of the said chemical inertness, the decomposition productsdo not tend to combine or amalgamate with the stylus and conse quentlyare more readily removed therefrom by being heated to their fusiontemperatures. Because of the characteristics of the stylus member A,this high temperature may be attained without danger to the stylusitself.

It will therefore be seen that the life of the stylus will be determinedalmost exclusively by the life of the heating element B. It is apparentthat the element B must be heated to a higher temperature when my stylusmember A is employed than when the wire 2 itself is the stylus. Sincethe wire 2 is no longer in contact with the heat-sensitive surface, thedeteriorative effect thereon of the decomposition products of theheat-sensitive surface is negligible, only such residues as sputter orjump from the surface suillciently to attach themselves to the wire 2being w) affected. However, progressive oxidation can still take place.

In order to more fully protect the wire 2, it is preferably encased by asuitable refractory cement indicated by the broken lines 6 of Fig. 1.This cement not only serves to fix the stylus member A Within the coiledwire 2 but also simultaneously serves to seal the wire from the actionof all ex ternal deteriorative influences. In addition, it improves theheat transfer characteristics between the Wire 2 and the stylus member Aby preventing direct heat radiation from the wire 2 and, because of itsrefractory nature, substantially inhibiting heat transfer to theatmosphere therefrom.

The embodiment illustrated in Fig. 2 presents certain advantages overthe simpler construction of Fig. 1. In Fig. 2, the stylus member A ishollowed as at 8 and into the cavity thus formed is placed the wire 2which constitutes the heating element B. The cavity is then filled withrefractory cement 6. It will be apparent that this constructionmaterially improves the heat transfer characteristics between theheating element B and the stylus member A since substantially all of theheat generated by the resistance wire 2 is transferred to the stylusmember A. This reduces the temperature to which the wire 2 need beheated and thus prolongs its life.

In addition, since the refractory cement 5 is generally lighter than thehard material of which 75 the stylus member A is composed, the weight ofthe stylus member A is somewhat decreased, thus decreasing its inertiaand increasing the sensitivity of the stylus as a whole. This is ofparticular importance where the stylus is employed in sensitivemeasuring instruments.

Furthermore, the cement 6 is by this construction itself insulated andprotected from the deteriorative effects of the decomposition productsof the heat-sensitive surface. This is particularly important whensilicious cements are em ployed. The effect of the decompositionproducts on the cement is such as to cause it to crumble 0r flake off,thus exposing the wire 2 to the deteriorative effects which theapplication of the cement 6 is designed to prevent. In the embodiment ofFig. 2, the cement is so positioned as to make it practically impossiblefor decomposition products to attack and destroy it.

It will be apparent that by constructing the heated stylus in the mannerdescribed, I have eliminated the disadvantages of styluses previouslyemployed with heat-sensitive surfaces and have devised a stylus which isat once simple,

effective and of long life. Many changes may of course be made in thespecific design of the stylus without departing from the spirit of theinvention as set forth in the following claims.

I claim:

1. A two-piece stylus for inscribing on a heatsensitive surfacecomprising a heat absorbing and transmitting stylus member and a heatingelement therefor, said stylus member being formed of a substance fromthe group consisting of natural and artificial gems and silicon carbide.

2. A two-piece stylus for inscribing on a heat sensitive surfacecomprising a heat absorbing and transmitting stylus member and anelectrical heating element therefor comprising heat resistant wire ofhigh electrical resistance, said stylus member being formed of asubstance from the group consisting of natural and artificial gems andsilicon carbide.

3. The two-piece stylus of claim 2, in which the Wire at least partiallyenvelops the exterior of said stylus member and is covered by arefractory cement, the cement thus serving to fasten the wire to thestylus member and simultaneously to seal the wire from the action ofexternal deteriorative influences.

4. The two-piece stylus of claim 3, in which the stylus member is formedof a gem.

5. The two-piece stylus of claim 3, in which the stylus member is formedof aluminum oxide.

6. The two-piece stylus of claim 3, in which the stylus member is formedof a diamond.

'7. The two-piece stylus of claim 3, in which the stylus member isformed of silicon carbide.

8. The two-piece stylus of claim 1, in which the stylus member is formedof a gem.

9. The two-piece stylus of claim 1, in which the stylus member is formedof aluminum oxide.

10. The two-piece stylus of claim 1, in which the stylus member isformed of a diamond.

11. The two-piece stylus of claim 1, in which the stylus member isformed of silicon carbide.

12. A two-piece stylus for inscribing on a heatsensitive surfacecomprising a heat absorbing and transmitting stylus member formed of agem and having a recess, an electrical heating element therefor of heatresistant wire having high electrical resistance which is receivedwithin said recess, and refractory cement filling said recess forfastening said wire to said stylus member and sealing it Within saidrecess.

13. A two-piece stylus for inscribing on a heatsensitive surfacecomprising a heat absorbing and transmitting stylus member formed ofaluminum oxide and having a recess, an electrical heating elementtherefor of heat resistant wire having high electrical resistance whichis received within said recess, and refractory cement filling saidrecess for fastening said wire to said stylus member and sealing itwithin said recess.

14. A two-piece stylus for inscribing on a heat sensitive surfacecomprising a heat absorbing and transmitting stylus member formed of adiamond and having a recess, an electrical heating element therefor ofheat resistant wire having high electrical resistance which is receivedwithin said recess, and refractory cement filling said recess forfastening said wire to said stylus member and sealing it within saidrecess.

15. A two-piece stylus for inscribing on a heatsensitive surfacecomprising a heat absorbing and transmitting stylus member formed ofsilicon carbide and having a recess, an electrical heating elementtherefor of heat resistant wire having high electrical resistance whichis received within said recess, and refractory cement filling saidrecess for fastening said wire to said stylus member and sealing itwithin said recess.

GREGORY HALPERN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,200,810 Clemens Oct. 10, 19161,395,635 Finizio Nov. 1, 1921 1,656,690 Blackburn Jan. 1'7, 19282,031,532 Goldman Feb. 18, 1936 2,248,057 Bond July 8, 1941 FOREIGNPATENTS Number Country Date 246,565 Great Britain Jan. 28, 1926

